Flow Obstacles Research Articles

Analisis Kinerja dan Tingkat Pelayanan Ruas Jalan Raya Ciomas Kreteg Kabupaten Bogor

The development of transportation has an impact on increasing traffic flow. The increase in the number of vehicles and high levels of human movement will cause congestion if it is not balanced with adequate road infrastructure. The aim of the research is to identify the level of service and performance of road sections. Methodology is a method or technique used to test the validity of using certain research. The research location is on Jalan Raya Ciomas Kreteg, Bogor Regency because it is a residential and commercial area so it is busy every day. Data collection techniques are taken through surveys of geometric conditions, traffic flow, speed and side obstacles. The supporting data is obtained from the population according to the Central Statistics Agency. The survey was carried out during rush hour and it was discovered that the traffic volume was 1216.75 pcu / hour. The analysis results show that the capacity of Jalan Raya Ciomas Kreteg is 2201.45 pcu / hour and DS is 0.55, so the Jalan Raya Ciomas Kreteg section is in class C in the classification of road service levels.

Development and application of wellbore flow assurance monitoring system for combustible ice production in deepwater

The commercial development of combustible ice, as the most promising strategy energy, requires not only efficient gas production technology but also a safe flow assurance system. For the depressurization development of combustible ice in the sea area, the issues of wellbore fluid carrying sand, hydrate re-formation in the wellbore, and instability of wellbore flow, are the key problems leading to flow obstacles in the wellbore and affecting the normal production. Therefore, some measures must be taken to effectively monitor and analyze the flow situation in the wellbore during the development of combustible ice in the sea. In this paper, a Wellbore Flow Assurance Monitoring System (WFAMS) is developed to display the fluid flow conditions in the wellbore in real-time during the gas hydrate production, including temperature, pressure, flow rate, the carrying sand amount, etc. Furthermore, the system is capable of online monitoring for potential plug risks, including sand plugs and hydrate blockages caused by gas hydrate formation, as well as assessing flow stability. Additionally, it can provide valuable information, such as production adjustment data and the required injection dosage of thermodynamic inhibitors to prevent hydrate formation. In the 2020 South China Sea production test, this system was used for depressurization production and successfully predicted wellbore flow conditions. This enabled field engineers to monitor flow risks and adjust production plans in a timely manner, ensuring smooth test progress.

ANALISIS PENYEBAB KEMACETAN LALU LINTAS PADA JALAN KOLEKTOR PRIMER KABUPATEN BADUNG

The development of an area can be seen in the development of its transportation system. The Canggu village area is an area experiencing rapid development which has an impact on traffic density. The Canggu highway is one of the roads that serves the tourist area corridor, with heavy traffic flow poor road geometric conditions, and side obstacles that reduce road capacity. The purpose of this research is to analyze the perceptions of people who live along the Canggu highway corridor regarding the factors causing traffic congestion in the Canggu Village area. Primary data was obtained by observation and distributing questionnaires containing closed questions to 400 respondents. The data analysis method uses multiple linear regression statistics. The results of the analysis show that traffic flow, road geometrics, and side obstacles have a significant partial and simultaneous effect on traffic congestion on the Canggu highway section. Obtained Model Equation: Y=1.514+0.378X1+0.363X2+0.304X3+e, where traffic flow has the greatest influence compared to road geometry and side obstacles. The model's ability to predict is very strong as indicated by the coefficient value. determination (R2) was 89.1%.

ROME. IV. An Arecibo Search for Substellar Magnetospheric Radio Emissions in Purported Exoplanet-hosting Systems at 5 GHz

Plasma flow–obstacle interactions, such as those between an exoplanet’s magnetosphere and the host star’s stellar wind, may lead to detectable radio emissions. Despite many attempts to detect magnetospheric (auroral) radio emissions from exoplanets, a reproducible, unambiguous detection remains elusive. This fourth paper of the Radio Observations of Magnetized Exoplanets (ROME) series presents the results of a targeted radio survey of nine nearby systems that host exoplanet, brown dwarf, or low-mass-stellar companions conducted with the Arecibo radio telescope at ∼5 GHz. This search for magnetospheric radio emissions has the greatest sensitivity (∼1 mJy during <1 s integration times) and collected full Stokes parameters over the largest simultaneous bandpass of any survey to date. It is also the first survey to search for radio emission from brown dwarfs of spectral class Y, which may illuminate open questions regarding their magnetism, interior and atmospheric structure, and formation histories. No magnetospheric radio emissions from substellar companions were detected. These results are examined within the context of recent theoretical work on plasma flow–obstacle interactions, and radio emissions observed from the solar system planets and ultracool dwarfs.

Pemodelan 2D Daerah Rawan Banjir Sungai Lepo – Lepo Kota Kendari

Research was carried out to see the potential for flooding through Computational Fluid Dynamic simulations, namely a set of methodologies that allow computers to provide numerical simulations of fluid flow. The entire system is transformed into virtual form, and can be visualized via computer. Components in fluid dynamic computing include selection of mathematical models, discretization, numerical analysis schemes, numerical solutions and representation of processes numerically and graphically. Flood mapping can provide information about which areas need special attention so that it can be used as a reference in making policies related to flood management and can be used to increase wider public awareness regarding floods. The HEC-RAS permanent flow module is able to take into account the influence of various flow obstacles, such as bridges, culverts, bends, or obstacles on riverbanks. The permanent flow module is designed for use in riverbank management environments and the determination of flood risk insurance regarding the determination of riverbanks and floodplains. The permanent flow module can also be used to estimate changes in water level due to channel improvements or embankment construction. HEC-RAS permanent flow special module features include double plan analysis, double profile calculation, double culvert or gate analysis, flow optimization, and stable channel design and analysis. From the simulation results and depth classification, information on the area of inundation and areas prone to flood inundation on the Lepo-Lepo River is 29.34 Ha.

Development and performance evaluation of chitosan-graft-poly (N-vinyl pyrrolidone) as a dual-function inhibitor for hydrate decomposition and reformation

In the process of drilling and producing natural gas hydrates, the hydrate is prone to decomposition, leading to wellbore instability and well control problems, and the natural gas produced by the decomposition is prone to form hydrate again in the low-temperature and high-pressure wellbore, creating flow obstacles. The existing inhibitors, however, fail to effectively inhibit the decomposition and reformation of hydrates. In this work, N-vinylpyrrolidone was used to modify chitosan, and an inhibitor namely DFHI with a dual function of inhibiting hydrate decomposition and reformation was developed. The inhibitory effects of DFHI were analyzed using the optimized experimental method for evaluating hydrate decomposition and reformation, and the mechanism was analyzed. The results showed that the memory effect of hydrate reformation gradually weakened or even disappeared with the rising ambient temperature during hydrate decomposition. The inhibitory performance of DFHI exhibited a positive correlation with its concentration. 0.5% DFHI resulted in a 74.7% delay in the decomposition time of methane hydrate, along with an extension of the induction time for both hydrate formation and reformation by 137.2% and 262.1%, respectively, significantly weakening the memory effect of hydrate reformation. The mechanism of DFHI inhibiting hydrate decomposition primarily involves surface adsorption on hydrates and thickening effects that retard mass and heat transfer processes. During the process of hydrate formation and reformation, DFHI molecules tend to aggregate at the surface of methane bubbles, hindering gas–water contact and diffusion, particularly when numerous micro-nano bubbles generated by hydrate dissolution are present; furthermore, the adsorption of DFHI molecules on the surface of hydrates delays their nucleation and growth.

Fast urban inundation simulation with RIM2D for flood risk assessment and forecasting

IntroductionUrban pluvial flooding is a growing concern worldwide as consequence of rising urban population and climate change induced increases in heavy rainfall. Easy-to-implement and fast simulation tools are needed to cope with this challenge.MethodsThis study describes the development of the parsimonious, GPU-accelerated hydraulic model RIM2D for urban pluvial flood simulations. This is achieved by considering the built-up urban area as flow obstacles, and by introducing capacity-based approaches to consider urban drainage by infiltration on pervious surfaces and sewer drainage from roofs and sealed surfaces. The model performance was analyzed by simulating 8 heavy rainfall events in a test area in the city of Dresden, Germany. For these events detailed discharge measurements of sewer discharge are available, providing a unique dataset for evaluating the sewer drainage simulation, which is of high importance for realistic pluvial inundation simulations in urban areas.Results and discussionWe show that the model simulates the temporal dynamics of the sewer discharge and the sewer volume within acceptable ranges. Moreover, the erratic variation of the simulated to measured sewer discharge suggests that the deviations from the measurements are caused by the precipitation input rather than the model simplifications. We conclude that RIM2D is a valid tool for urban inundation simulation. Its short simulation runtimes allow probabilistic flood risk assessments and operational flood forecasts.

Numerical and experimental analysis of magneto-convective flows around pipes

Liquid metal flows exposed to intense magnetic fields play a fundamental role in the development of blankets for nuclear fusion reactors, where they serve to produce the plasma-fuel component tritium and transport the generated heat. When the liquid metal circulates in the blanket, it interacts with the plasma-confining magnetic field leading to the induction of electric currents. Electromagnetic forces and thermal buoyancy affect significantly velocity and pressure distributions. The resulting magneto-convective flow has peculiar features that have to be taken into account in order to evaluate heat transfer properties in the liquid metal. In the breeding zone of the water-cooled lead lithium blanket concept, the volumetric heat released in the liquid metal is removed by water-cooled circular pipes that represent obstacles for the liquid metal flow. In order to improve the understanding of the underlying physical phenomena and obtain a database for code validation, model experiments have been performed to investigate magneto-convective flow and heat transfer at two differentially heated parallel horizontal tubes immersed in a box filled with liquid metal. Among other properties, electric potential has been recorded on the surface of the test-section and compared with 3D numerical simulations. Computational results provide the basis for interpretation of the measured data, since they allow differentiating between flow-induced electric potential and thermoelectric effects.

Fiber reorientation due to obstacles in open channel flow

A model along with experimental validation is presented for fiber re-orientation within the flow of a thin fluid layer down an inclined plane. Unlike the usual approach (Jeffery), the model accommodates the fast-changing velocity gradient defying linearization and the flow constraints due to the thin thickness of the fluid film. Model equations are formulated, and the algorithm for the fiber rotation is developed. The velocity field within the channel is obtained, using COMSOLTM multiphase simulation. The formulated model equations are used to track the orientation of a single fiber. The spatial fiber orientation state is described in terms of the second order tensor by tracking multiple individual fibers with different initial orientations. To validate the model's predictions, an experimental setup was fabricated to record individual fiber kinematics during the flow and to describe the orientation of fibers in the open channel. A novel benchmark for assessing fiber re-orientation models is presented, wherein the dynamics of fiber orientation is observed in response to a semicircular obstacle within the fluid flow. The experimental results are compared to model predictions and are in reasonable agreement. Despite the simplified approach, both the dynamic of single fiber and the development of fiber orientation distribution due to the obstacle can be reasonably predicted.

Study on the hydrogen leakage diffusion behavior by obstacles in confined spaces

In this paper, a combination of experimental and numerical simulation is used to investigate the effects of obstacles and leakage hole shapes on the leakage diffusion pattern and hydrogen concentration. A small-size cubic geometry model of 0.47 m × 0.33 m × 0.20 m is used to calculate the concentration of the leakage model in the confined environment. The results show that the influence of the Q1-Turbulent Flow obstacle model on hydrogen leakage and diffusion is more serious than that of the Q2-Laminar Flow, the gas in the upper part of the model is easier to accumulate, the hydrogen concentration is higher, and it takes longer to finally reach a stable state. Rectangular leakage holes have a larger hydrogen diffusion range, faster diffusion rate, higher initial kinetic energy, and are more likely to exceed the lower flammability limit of hydrogen. Q1-Turbulent Flow obstacle modeling injection process, t = 0.3 s, the gas cloud just contacted the obstacle, initially spread along the obstacle. With the continuous leakage of hydrogen, a large amount of gas comes into contact with the obstacle, and at t = 0.5 s, the obstacle starts to block the normal diffusion of leaking hydrogen, causing initial kinetic energy loss under the effect of buoyancy and obstacle blocking, and the direction of motion of hydrogen changes. When t = 0.8 s, due to the blocking effect of the obstacle wall, aggregation and vortex area are generated. t = 1 s, the area of vortex area is further increased, at this time, the degree of danger is obviously higher than before, and it is very easy to asphyxiation, explosion and other accidents.

Anchoring Effect of an Obstacle in the Silo Unclogging Process.

Contrary to the proven beneficial role that placing an obstacle above a silo exit has in clogging prevention, we demonstrate that, when the system is gently shaken, this passive element has a twofold effect in the clogging destruction process. On one side, the obstacle eases the destruction of weak arches, a phenomenon that can be explained by the pressure screening that it causes in the outlet proximities. But on the other side, we discover that the obstacle presence leads to the development of a few very strong arches. These arches, which dominate in the heavy tailed distributions of unclogging times, correlate with configurations where the number of particles contacting the obstacle from below are higher than the average; hence suggesting that the obstacle acts as an anchoring point for the granular packing. This finding may help one to understand the ambiguous effect of obstacles in the bottleneck flow of other systems, such as pedestrians evacuating a room or active matter in general.

ROME. III. The Arecibo Search for Star–Planet Interactions at 5 GHz

After nearly three decades of discovery, many exoplanetary systems have been studied and characterized in detail with one important exception: exoplanet magnetism. Although many surveys sought to detect magnetospheric radio emissions from exoplanets to directly measure their magnetic field strengths, they have yet to reveal an unambiguous detection. However, the indirect detection of exoplanet magnetic fields by measuring their influence on their host stars via magnetic star–planet interactions has recently gained prominence as an alternative method of discovery. This third paper of the Radio Observations of Magnetized Exoplanets series presents the results of a targeted radio survey of eight nearby exoplanet-hosting systems that may engage in star–planet interactions. This survey, conducted with the Arecibo radio telescope at ∼5 GHz, has the greatest frequency coverage of any to date while providing millijansky-level sensitivity over <1 s integration times. No exoplanet-induced stellar radio bursts were detected. The orbital phase coverage of candidate systems for magnetic star–planet interactions is described, and the survey results are examined within the context of the plasma flow–obstacle paradigm and searches for star–planet interactions at other wavelengths.

A numerical study on the effects of using combined flow fields and obstacles on the performance of proton exchange membrane fuel cells

AbstractThe flow field structure has an important influence on the comprehensive performance of the proton exchange membrane fuel cell (PEMFC). This research investigates the effects of combined flow fields on the distribution of species concentration, the pressure drop, and the overall performance of PEMFC based on the polarization curve and power consumption ratio (PCR). Obstacles are arranged in different areas to study the mass transfer of the gas inside the combined flow field. The results show that the combined serpentine flow field improves the concentration distribution of species and the performance of the cell is enhanced with the increase of the proportion of the single‐channel serpentine structure in the combined flow field, but the PCR is decreased. The energy efficiency conversion in the low voltage region is better when the obstacles are arranged in the entire flow field. Moreover, the vortex effect generated by the obstacles enhances the convection ability under the rib parallel to the inlet direction, while the transverse vortex and secondary flow perpendicular to the inlet direction are weakened by the flow field structure so that the mass transfer of gas is enhanced.

A parametric geometry model of the aortic valve for subject-specific blood flow simulations using a resistive approach

Cardiac valves simulation is one of the most complex tasks in cardiovascular modeling. Fluid–structure interaction is not only highly computationally demanding but also requires knowledge of the mechanical properties of the tissue. Therefore, an alternative is to include valves as resistive flow obstacles, prescribing the geometry (and its possible changes) in a simple way, but, at the same time, with a geometry complex enough to reproduce both healthy and pathological configurations. In this work, we present a generalized parametric model of the aortic valve to obtain patient-specific geometries that can be included into blood flow simulations using a resistive immersed implicit surface (RIIS) approach. Numerical tests are presented for geometry generation and flow simulations in aortic stenosis patients whose parameters are extracted from ECG-gated CT images.

The use of machine learning in optimizing the height of triangular obstacles in the mixed convection flow of two-phase MHD nanofluids inside a rectangular cavity

In this article, a numerical study was conducted on the mixed convection (CNV) of nanofluid (NFD) in a two-dimensional rectangular cavity using the control volume method. The upper and lower walls of the cavity were cold and hot, respectively, and its two vertical walls were insulated. The Upper wall has constant velocity and order to create a forced CNV in the cavity. They positioned three triangle-shaped obstacles on the heated wall that were likewise hot. The velocity and temperature graph values in the cavity, the velocity and streamline contours, and the Nusselt number value were examined independently by varying the height (HIT) of each barrier. Using artificial intelligence, the best values of the parameters to have the strongest flow and the most heat transfer (HTF) were checked. Two-phase method was used to simulate NFD flow. The results of this study showed that the middle obstacle with the highest HIT had more HTF. Increasing the length of the obstacle on the right has reduced the amount of HTF and the highest HTF occurred at the lowest HIT of this obstacle. When the obstacle on the left side has the HIT, the amount of HTF is the highest, while its average value has minimized the HTF. An increase in the HIT of the right fin at different HITs of the other two fins reduces the average Nu value

Research on methane hydrate formation in porous media with gas–water two-phase flow

The study of hydrate formation in porous media is crucial for the efficient production of natural gas hydrate. Current research on gas hydrate formation in porous media has primarily focused on the static state. A prediction model of hydrate formation under the condition of gas–water two-phase flow was established by combining the heat transfer and gas–water two-phase flow mechanisms in porous media. Methane hydrate formation in quartz sand was experimentally investigated under a gas–water two-phase flow. The results revealed an obvious pressure difference with hydrate formation at different positions; the pressure difference increased with time, which can be used as an important basis to assess the distribution of flow obstacles in porous media. COMSOL Multiphysics was used to solve the proposed model, and the accuracy of the model prediction results was verified using the experimental data. Further, the hydrate formation process and evolution law in the experiment were simulated and inverted. Flow parameters, such as pressure, hydrate saturation, and water saturation, presumably exhibit non-uniform distributions with the formation of hydrates in porous media. The longer the time, the more distinct the non-uniform distribution of the aforementioned parameters and the higher the risk of flow obstacles in porous media. This study provides an important theoretical basis for the efficient development of natural gas hydrate in the future.

Spawning migration behaviour of sea trout (Salmo trutta L.) in a boreal river system: effects of flow conditions and obstacles on migratory activity.

In this study, radio telemetry was used to examine the upstream spawning migration behaviour of anadromous brown trout (sea trout), Salmo trutta L., in a boreal river system, the River Isojoki, western Finland. The aim was to study the movement activity and migration characteristics of trout during the upstream spawning migration, as well as to locate the important spawning habitats and study the spawning characteristics. Furthermore, the authors analysed how flow conditions and a hydropower dam, with adjacent fishways, affected the upstream spawning migration. Tagged trout spawned in both the main stem and four tributaries, with spawning taking place from early October to November. The movement activity of radio-tagged trout was influenced by a hydropower dam (Perus dam), with spring migrators spending prolonged periods at the dam area, postponing the migration upstream. Flow conditions affected the total time spent at the dam area, as well as the movement activity in the free-flowing sections above the dam, with increasing flow stimulating activity. In addition, time of river ascent and location of spawning area had a significant effect on the movement activity of tagged trout. These results are further evidence that synergistic effects of flow and migratory obstacles can negatively influence migrations of anadromous fish, regardless of constructed fishways. The management of flow regimes and the efficiency of fishways are vital, as climate change will likely influence the flow and increase the water temperature of boreal river systems, further aggravating issues caused by obstacles.

Gravity-resisting colloidal collectives.

Self-assembly of dynamic colloidal structures along the vertical direction has been challenging because of gravity and the complexity in controlling agent-agent interactions. Here, we present a strategy that enables the self-growing of gravity-resisting colloidal collectives. By designing a unique dual-axis oscillating magnetic field, time-varying interparticle interactions are induced to assemble magnetic particles against gravity into vertical collectives, with the structures continuing to grow until reaching dynamic equilibrium. The collectives have swarm behavior and are capable of height reconfiguration and adaptive locomotion, such as moving along a tilted substrate and under nonzero fluidic flow condition, gap and obstacle crossing, and stair climbing.

Numerical investigation of heat transfer performance of an air heater with delta flow obstruction

Air heaters are a vital component in many engineering systems, including room heating and agricultural dryers. The use of flow obstacles improves the convective heat transfer coefficient by interrupting the formation of a laminar sub-layer. In the previous studies reported, the thermal and frictional effects of various flow obstacle geometries were studied, but they are limited to non-inclined obstacles. The current research examines the thermal and hydraulic characteristics of air heaters with inclined and non-inclined delta shape obstacles using numerical techniques and compares the results with empirical predictions and literature data. The influence of flow rate and angle of attack (α) on Nusselt number (Nu) and friction factor (f) were evaluated using CFD for Reynolds numbers (Re) ranging from 5000 to 20,000 and for α ranging from 300 to 900. A rectangular duct (300 mm × 50 mm) with a constant heat flux of 800 W/m2 at the bottom surface of the air heater with delta obstructions of relative obstacle height (e/H) of 0.5 with a constant transverse (Pt/b) of 1.5 and longitudinal pitch (Pl/e) of 3 was considered. The Nu, f and Thermal Enhancement Factor (TEF) were calculated and investigated for various flow rates and attack angles. The predicted Nu and f values demonstrated a good agreement with empirical correlations, with an average variation of 5.68 percent and 7.2 percent, respectively. The CFD results were also consistent with earlier published experimental findings. The results indicate that using a delta obstruction enhances heat transfer rate considerably at the cost of increased pressure loss. The use of delta-shaped flow obstruction increases Nusselt number in the range of 71–162, with a 6–9.6 times increase in friction factor. A maximum TEF of 1.69 was obtained for the air heater with delta obstruction with α = 300 at Re = 5000.

IDENTIFIKASI PENYUMBATAN ALIRAN AIR PADA PIPA DENGAN METODA GETARAN

The piping system design due to pressure will experience vibrations due to the excitation force that comes from the pump. Excitation force occurs due to changes in fluid flow velocity. In addition, the length of the pipe and the large number of bends of the pipe due to cross with other installations, cause vibrations in the pipe. vibration analysis in the pipe should not be underestimated, where it is necessary to identify the causes of vibration in the pipe due to flow and placement of good support and the effect of obstacles in the pipe flow to prevent failure of the pipe. In addition, clogging of pipelines can result in reduced system carrying capacity, wastage of energy and resources, and the potential for increased likelihood of environmental and health problems. Therefore, this study will discuss the identification of blockage of water flow in pipes using the vibration method. The excitation force comes from the fluid flow flowing in the pipe, while the vibration response is generated using the accelerometer sensor provided with the FFT Analyzer. Retrieval of data using the accelerometer as a vibration sensor served by Ono Sokki's FFT analyzer which is then analyzed using Matlab. Installation with four supports shows that the resonance that occurs in the installation of two supports can be reduced, but it causes the magnitude of the iron pipe to increase, while the PVC pipe decreases at a frequency of 5 Hz. In general, the result of installing four supports shows that the noise on the PVC pipe is reduced while the iron pipe is getting higher due to the installation of a barrier in the pipe due to water flow. The vibration pattern that occurs uses a harmonic response simulation, the vibration pattern that occurs uses a harmonic response simulation.